3D solvent-responsive actuator capable of directionally outputting thrust

The realization of actuators that can output thrust is critical for improving the comprehensiveness of actuator functions and broadening the range of soft robot applications. Thrust actuation can be achieved by the volume expansion of active materials under the stimulus, but most expandable materials suffer from the low rate of volume change and/or uncontrollable expansion directions. Here, we design a 3D network of carbon nanotubes with gradient stiffness. By synergistically utilizing the different responses of each stiffness layer to solvent stimuli, a solvent-responsive actuator that can deform rapidly and output thrust directionally is prepared. By adjusting the parameters of the actuator, it can achieve a variety of complex actuations such as multidirectional actuation, multifunctional actuation, sequential actuation, and programmable actuation.